Spent some time over the last month building out an integration for WooCommerce & Easypost, since I liked their product. I am pretty happy with the outcome, looking to get some feedback from users once posted over on the directory. Seems to be going well already have 30+ downloads in one day.
I toyed with the idea of selling it commercially, in the end I am open sourcing it. I think both of these products are of the highest caliber.
Have a look at EasyPost at https://www.easypost.com/.
Check the plugin it out on GitHub or WordPress